SOLUTION: Sandra is rowing a canoe. Her rate of speed in still water is 6 miles per hour. It takes her 3 hours to travel 10 miles round trip. If she rows at a constant speed, determine the r

Let v be the rate of current, in miles per hour.


Notice that one way distance is 5 miles.


Then Sandra's rate rowing downstream is (6+v) miles per hour, and the time rowing 6 miles downstream is  hours.


Sandra's rate rowing upstream is (6-v) miles per hour, and the time rowing 6 miles upstream is  hours.


The time equation is

 +  = 3   hours.


To solve it, multiply both sides by (6+v)*(6-v). You will get

5*(6-v) + 5*(6+v) = 3*(6^2-v^2),

60 = 108 - 3v^2  ====>  3v^2 = 108 - 60 = 48  ====>  v^2 =  = 16  ====>   v = 4 miles per hour.


Answer.  The rate of the current is  4 mph.